In recent years, transceivers used in optical communications have often included a digital signal processing circuit. As an example, a receiver front end circuit generates an electric field information signal indicating electric field information of a received optical signal. The digital signal processing circuit recovers data from the electric field information signal. In addition, the digital signal processing circuit generates an electric field information signal indicating electric field information of an optical signal from client data according to a modulation scheme. A transmitter frontend circuit generates a modulated optical signal according to the electric field information signal.
On the other hand, functions and/or performances (hereinafter simply referred to as “functions”) that are requested in a communication system differ according to an application. As an example, quality, capacity, transmission distance, spectrum utilization efficiency, and the like are requested for each user. These requests can be achieved by a digital signal processing circuit included in a transceiver. As an example, large-capacity transmission (or long-distance transmission) is achieved by using a digital signal processing circuit that provides high-performance error correction. In addition, long-distance transmission is achieved by using a digital signal processing circuit that provides high-performance dispersion compensation/non-linear compensation.
A technology relating to a signal processing circuit is described, for example, in Japanese Laid-open Patent Publication No. 63-221708 and Japanese Laid-open Patent Publication No. 6-112854.
Requests from all users can be satisfied by developing a digital signal processing circuit that provides all of the functions requested in a communication system. However, in this case, the circuit scale of the digital signal processing circuit increases, and therefore it may be difficult to design the circuit, and a manufacturing yield may deteriorate. Further, the power consumption of the digital signal processing circuit increases.
The problem above can be solved by developing a digital signal processing circuit that corresponds to each of the requested functions. However, in this case, plural types of digital signal processing circuits are developed, and therefore the total development time and the total development cost may increase.